In 2011, an estimated 19% of U.S. adults were current smokers (43.8 million people), and an estimated 950 children become addicted to smoking daily. Smokers vary widely in terms of their daily nicotine intake, ranging from “social smokers” who may only consume 1 or 2 cigarettes in the presence of friends and/or with alcohol, to heavy smokers who consume 60 or more cigarettes per day.
A number of costs are associated with smoking. For example, during 2000-2004, cigarette smoking was estimated to be responsible for $193 billion in annual health-related economic losses in the United States (nearly $96 billion in direct medical costs and an additional $97 billion in lost productivity). See Centers for Disease Control and Prevention. Smoking-Attributable Mortality, Years of Potential Life Lost, and Productivity Losses-United States, 2000-2004. Morbidity and Mortality Weekly Report 2008; 57(45):1226-8. Half of smokers will die from their habit.
Nicotine from smoked cigarettes is delivered to the smoker's lung. Nicotine laden smoke particles from combustible tobacco products can be carried proximally on tar droplets (0.1-1.0 μm in diameter). These particles can be inhaled and travel to the small airways and alveoli in the deep lung. Nicotine can off-gas from the particles and defuse to, and deposit on, the alveoli wall where it can be rapidly absorbed into the blood stream.
An electronic cigarette can be used to simulate and substitute for tobacco smoking. However, electronic cigarettes can create aerosol particles in a size range too small to gravitationally settle in the alveoli of the deep lung. As a result, little or no nicotine delivered by an electronic cigarette can enter the circulatory system. Some nicotine delivered by an electronic cigarette can be slowly absorbed through the gastrointestinal (GI) tract and the buccal tissues of mouth and throat. The pharmacokinetics of nicotine delivered via electronic cigarettes can be much slower than the pharmacokinetics of nicotine delivered by smoked cigarettes; as such, electronic cigarettes can be ineffective in treating acute nicotine cravings.
A need exists to control nicotine particle size generated from an electronic nicotine delivery device (e.g., electronic cigarette) to ensure deep lung absorption of nicotine. Aerosol particles with a mass median aerodynamic diameter of about 1 μm to about 5 μm can be small enough to reach the deep lung but large enough to gravitationally settle in alveoli, which can result in a rapid pharmacokinetics (PK). With an increase in the particle size, the amount and speed of nicotine absorption can more closely mimic that of smoked cigarettes and can help to reduce nicotine cravings and more generally provide a reinforcing experience for users.